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UNITED STATES PATENT OFFICE.

DANIEL B. GRANDY, OF BOSTON, MASS., ASSIGNOR TO NATHANIEL F POT- TER,TRUSTEE FOR HIMSELF, SAID GRANDY, FRANK hIAURAN, OHAS. Gr. MCKNIGHT, ANDGEORGE OHATTERTON, OF PROVIDENCE, R. I.

DUPLEX TELEGRAPH.

SPECIFICATION forming part of Letters Patent No. 230,001, dated July 13,1880.

Application filed December 4, 1879.

To all whom it may concern Be it known that I, DANIEL B. GRANDY, ofBoston, county of Suffolk, State of Massachusetts, have invented anImprovement in Duplex Telegraphs, of whichthe following description, inconnection with the accompanying drawings, is a specification.

My invention relates to a duplex telegraph in which I render the relayinsensible to signals sentfrom its own end of the line by means of amovable auxiliary electro-magnet which acts on the mainrelay-armature,.or a second armature mounted upon the samecarrying-lever in the opposite direction to the main magnet, therebyacting as a detent to prevent the main armature from approaching itsmagnet to give a signal when acted upon by the battery at its own endofthe line.

In the present embodiment of my invention 2o the main armature iscarried on a lever pivoted in front of its electro-magnet, and isprovided with a retracting-spring, as usual, while the auxiliary magnetis carried by a similar lever, pivoted just in front of the one carryingthe main armature, and is acted upon by a second retracting-spring, thecoils oi' the said auxiliary magnet being placed in circuit between themain battery and transmitting-key, (shown as a continuity-key, or one bywhich the line is 3o put to earth at the same moment that the battery istaken oi'.)

1f the main battery at the same end of the line, which I shalldenominate, for convenience, the home7 battery, is o-that is, with itscir- 3 5 cuit broken-the auxiliary magnet is inoperative, remaining heldback by its retractingspring, and the armature responds to impulses fromthe distant battery, as in a simple relay.

When the home battery is put on, the main 4o armature and auxiliarymagnet, being, as it were, bound together by the attractive force of thelatter, form a compound armature held back by the strength of bothretracting-sprin gs and drawn forward hy the iniluence of the homebattery on the relay-magnet, which is not enough to overcome bothsprings until aided by the battery of distant station, which is thusenabled to give a signal.

If desired, the coils of the auxiliary magnet may be in a localbatterycircuit operated si- 5o multaneously with the main battery by means of adouble-pointed transmitter or key.

Figure l is a side view of a relay embodying my invention; Fig. 2, a topview thereof;

Figs. 3 and 4, details showing diil'erent pos- 55 tions ofthe armatureand auxiliary magnet; and Fig. 5, a general view, showing the battery,instruments, and connections at one station.

The block a., sustaining the main electro- 6o magnet l) andworkingparts, is provided with the usual binding-screws for connectingthe different wires. The main armature is carried on a lever, c, pivotedat d, and provided with a contact-point, e, and retraeting-spring j'. 65

The stop-point g, held in the frame h, is tipped with insulatingmaterial, whereby, when the armature is up to its magnet or closed, thecircuit is broken between the lever c and framework 7L, to give asignalon the local repeater 7o and sounder, as usual.

When the armature is open its contact-point is connected with thestop-point i and framework h by the pin h in the arln l, pivoted at m,provided with a retracting-spring, n, and

carrying the auxiliary electro-magnet, 0, adapted to act on an armaturecarried by the lever c, so that when the current is passing through itscoils its attractive influence binds the levers c Ztogether, thus addingthe retracting 8o force of the spring 'n and preventing the now compoundarmature c from moving up under the influence of the home battery on themain relay-magnet. When in this position an impulse from the distantstation, co-operating with the current ofthe home battery, will attractthe armature and overcome the springs f and a, and draw it up, as shownin Fig. et.

It will be seen that the auxiliary magnet is merely a means ofautomatically attaching the 9o retracting-spring a to the main armaturewhen the home battery is on, and may consequently have any power greaterthan that of the spring n, which should about balance the force of thehome battery in the magnet b, thus always leaving the force of thespring fthe effective force to be overcome by the distant battery in allconditions ofthe home battery. The power O/ahe springs f n is adjustedby the capstans //p r, as usual.

The circuit of the usual local sounding-instrument is through thebinding-screws 2 3, frame-Workin pin k., and lever c, and may be brokenateither end ofthe pin lc to give a signal.

When the home battery is oft' the auxiliary magnet is inoperative, andthe instrument works as a simple relay, contact being made and broken ate, as in Fig. 3; but when the home battery is on the levers c and Z movetogether, and contact is made and broken at c'.

The main-battery circuit passes from binding-screw 4, through the coilsof the auxiliary magnet and binding-screw 5, to the key, and thence tobinding-screw 6, through the coils of the main magnet b, tobinding-screw 7, connected with the main line.

It' necessary, I may employ the usual conden sers to obviate the edectsoi'static discharge.

I claim- 1. In a mult-iple-transmission telegraph, the combination, withthe main relay-magnet and its armature, of a movable auxiliaryelectrolnagnet adapted to act on an larmature carried by the mainarmature-lever in an opposite direction to the main magnet,substantially as and for tlie purpose described.

2. In a multiple-transmission telegraph, a

main relay-magnet and its armature, combined with a movable auxiliarymagnet adapted to attract the main armature-lever and prevent it frombeing moved up to the poles of the re lay-magnet to give a signal whenacted upon by the home battery alone, the said auxiliary magnet being soadjusted as to its movement that when the force of the distant batteryis added the said auxiliary magnet moves with the main relayarmature tothe poles of the relay to give a signal, substantially as described.

3. In a multiple-transmission telegraph, the combination, With the mainelectro-magnet and its armature and retracting-spring, of an auxiliaryelectro magnet, a carrying -lever pivoted and provided with aretracting-spring capable lof being adj usted to balance the attractiveinfluence ofthe home battery, the said auxiliary magnet applying by itsattractive force its retractingspring when the home battery is incircuit, substantially as described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

DANIEL B. GRANDY.

Witnesses:

G. W. GREGORY, N. E. WHITNEY.

